• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.52.3-52.3
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• 2019

We present our first attempt at understanding the dual impact of the large-scale density and velocity environment on the formation of very first astrophysical objects in the Universe. Following the recently developed quasi-linear perturbation theory on this effect, we introduce the publicly available initial condition generator of ours, BCCOMICS (Baryon Cold dark matter COsMological Inital Condition generator for Small scales), which provides so far the most self-consistent treatment of this physics beyond the usual linear perturbation theory. From a suite of uniform-grid simulations of N-body+hydro+BCCOMICS, we find that the formation of first astrophysical objects is strongly affected by both the density and velocity environment. Overdensity and streming-velocity (of baryon against cold dark matter) are found to give positive and negative impact on the formation of astrophysical objects, which we quantify in terms of various physical variables.

• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.61-67
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• 2024

In this study, the behavior of water droplets on a solid-infused surface was evaluated by quantifying a water droplet's contact angle, sliding angle, and terminal velocity. The contact angle hysteresis and sliding angle of water on the solid-infused surface were measured to be lower than those of the hydrophobic PTFE surface. It led to the enhancement of the initiation of the water droplet's movement. When the capillary number was lower than Ca < 0.004, the terminal velocity of the water droplet on the solid-infused surface was higher than the PTFE surface due to the low contact line resistance. However, the transition of the droplet morphology from a hemispherical shape to a streamlined teardrop shape beyond Ca > 0.004 lost the effect of reducing frictional resistance on the solid-infused surface.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.145-153
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• 2011

In the system necessary for safety such as the train control system, to make train control information be sent correctly is very important to enable organic movement between trains. In the case of the system such as RF-CBTC (Radio Frequency Communication Based Train Control) the control related information is sent through wireless transmission between on-board system of a train and wayside transmitter. The wayside transmitter collects the running information such as location, velocity from the on-board system and operates the optimizing control by sending the control information such as the target, limited velocity to the on-board system. But, when the communication disconnect or train failure, the critical hazard such as train collision or derailment may be possible because the RF-CBTC depends on the information through wireless communication. This paper discribes of performing Fall-Back system to detect train position in the case of rail break or communication failure to avoid train accident and allows train to be operated safely. It can be implemented with ATP function through track circuits using active-type transformers and axle counters, and allows train to be operated manually in emergency status.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.146-151
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• 2016

In this paper, we present a method for estimating the ratio of CPA distance to velocity of underwater target using target bearing information in CPA situation. This ratio can be estimated by previous research which is Envelope CPA using proximity sensor but it has low performance if the target is close to receiver sensor or bigger interference caused by multi-path effects. Therefore we propose a Bearing CPA technique using a target bearing information as a way to overcome.

• Journal of Korea Multimedia Society
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• v.16 no.5
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• pp.619-628
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• 2013

In this paper, we describe a strongly improved tracking method using combination of CAMshift and Kalman filter algorithm. CAMshift algorithm doesn't consider the object's moving direction and velocity information when it set the search windows for tracking. However if Kalman filter is combined with CAMshift for setting the search window, it can accurately predict the object's location with the object's present location and velocity information. By using this prediction before CAMshift algorithm, we can track fast moving objects successfully. Also in this research, we show better tracking results than conventional approaches which make use of single color information by using both color information of HSV and YCrCb simultaneously. This modified approach obtains more robust color segmentation than others using single color information.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.301-304
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• 2006

As is different from formerly used fixing camera method in this paper, proposed method that can measure the speed of vehicles and logarithm of vehicles in video. Vehicles that proposed method runs with 50km/h, 80km/h, 90km/h's the speed recording on Video Tape beginning point and time of reaching point draw, and calculated 47.57km/h, 81.20km/h, the 90.00km/h speed by time and distance, the tracking cars and the velocity detection in video with the 'begin-line mark' and the 'end-line mark' processing.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.293-301
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• 2016

Objective: The purpose of this study was to analyze the effects of freezing of gait and visual information on the static postural control ability in patients with Parkinson's Disease (PD) during the bipedal stance with feet together. Method: This study included a total of 36 patients with PD; the freezer group included 17 PD patients (age: $69.3{\pm}6.2yrs$, height: $159.6{\pm}9.0cm$, weight: $63.4{\pm}9.78kg$) and the nonfreezer group included 19 PD patients (age: $71.4{\pm}5.6yrs$, height: $155.8{\pm}7.1cm$, weight: $57.7{\pm}8.6kg$). Static postural control ability was analyzed using variables of center of pressure (COP) and dividing by mediolateral, anteroposterior, and integration factors during a bipedal stance with the eyes open and closed. Results: Freezers and nonfreezers showed increases in anteroposterior velocity, mediolateral velocity, averaged velocity, and mediolateral 95% edge frequency when visual information was blocked. Additionally, freezers had greater anteroposterior range, 95% confidence ellipse area, and COP anteroposterior mean position than nonfreezers. Conclusion: Freezers and nonfreezers showed a reduction in static postural control ability when visual information was blocked. Additionally, the results of this study found a significant difference in static postural control ability between freezers and nonfreezers with PD. In particular, anteroposterior range, 95% confidence ellipse area, and COP anteroposterior mean position might be used to distinguish between freezers and nonfreezers with PD.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.9
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• pp.4491-4509
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• 2017

The present paper proposes a novel dynamic system for hand gesture recognition. The approach involved is comprised of three main steps: detection, tracking and recognition. First, the gesture contour captured by a 2D-camera is detected by combining the three-frame difference method and skin-color elliptic boundary model. Then, the trajectory of the hand gesture is extracted via a gesture-tracking algorithm based on an occlusion-direction oriented linear extrapolation predictor, where the gesture coordinate in next frame is predicted by the judgment of current occlusion direction. Finally, to overcome the interference of insignificant trajectory segments, the longest common subsequence (LCS) is employed with the aid of velocity information. Besides, to tackle the subgesture problem, i.e., some gestures may also be a part of others, the most probable gesture category is identified through comparison of the relative LCS length of each gesture, i.e., the proportion between the LCS length and the total length of each template, rather than the length of LCS for each gesture. The gesture dataset for system performance test contains digits ranged from 0 to 9, and experimental results demonstrate the robustness and effectiveness of the proposed approach.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.104-113
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• 2022

In this paper, we propose deep learning-based target distance and velocity estimation technique for OFDM radar systems. In the proposed technique, the 2D periodogram is obtained via 2D fast Fourier transform (FFT) from the reflected signal after removing the modulation effect. The periodogram is the input to the conventional and proposed estimators. The peak of the 2D periodogram represents the target, and the constant false alarm rate (CFAR) algorithm is the most popular conventional technique for the target's distance and speed estimation. In contrast, the proposed method is designed using the multiple output convolutional neural network (CNN). Unlike the conventional CFAR, the proposed estimator is easier to use because it does not require any additional information such as noise power. According to the simulation results, the proposed CNN improves the mean square error (MSE) by more than 5 times compared with the conventional CFAR, and the proposed estimator becomes more accurate as the number of transmitted OFDM symbols increases.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.133-149
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• 2003

The purposes of present study were to determine the major check-points of golf swing from the review of previous studies, and to suggest additional information on the teaching theory of golf. The golf swing motion of 6 male and female elite university golf players were filmed with 16mm Locam II high speed cameras at the speed of 200f/s, and variables such as time, displacement, angle, velocity were calculated and analyzed by 3D Cinematography using DLT method. The results were: 1. Differences were shown in the ratio of weight distribution on the feet, cocking angle, take-back velocity, club-head velocity at impact depending upon the physical characteristics and club used for swing. 2. Time for the down-swing and impact were $0.27{\sim}0.29s$ in men and $0.29{\sim}0.32s$ in women, which was 1/3 of the time for the back-swing. Women showed longer total swing time than men because of longer time in back-swing, follow-through and finish. 3. Men showed larger range of motion in shoulder and knee joints than women, on the other hand women showed larger range of motion in hip joint than men. 4. Cocking motion and right elbow flexion were occurred at the top of back-swing and cocking release was occurred at the moment of impact. Maximum rotations of shoulder and hip joints were found between the top of back-swing and down-swing phase. 5. Women showed lower back-swing velocity than men, and men showed higher club velocity(men: $38.2{\sim}38.6m/s$, women: $35.1{\sim}36.4m/s$) than women.